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Mechanistic study of Bu2SnCl2-mediated ring-opening polymerization of epsilon-caprolactone by multinuclear NMR spectroscopy.
- Source :
-
Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2003 Sep 22; Vol. 9 (18), pp. 4346-52. - Publication Year :
- 2003
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Abstract
- The ring-opening polymerization (ROP) of epsilon-caprolactone (CL) was carried out in toluene at 100 degrees C with n-propanol (nPrOH) in the presence of Bu(2)SnCl(2). It comes out that the molar mass of the polyester chains can be predicted from the initial monomer-to-alcohol molar ratio in accordance with a controlled ROP mechanism involving an O-acyl cleavage of the monomer to selectively form (alpha-propyloxy)(omega-hydroxy)poly(epsilon-caprolactone) chains. In order to gain fundamental understanding of the mechanistic factors governing the polyester chain growth, advanced (1)H, (13)C, and (119)Sn NMR investigations were performed in situ in [D(8)]toluene, as well as with model solutions that contained Bu(2)SnCl(2) and binary mixtures of the components at various concentrations and temperatures. This has enabled us to propose a mechanism in which Bu(2)SnCl(2) behaves as a catalyst, while nPrOH is the actual initiator. It involves non-aggregated, six-coordinate Bu(2)SnCl(2) complexes in which ligands exchange fast on the (119)Sn NMR observational timescale, and the simultaneous interactions of CL and alcohol function in such a way that it favors insertion/propagation reactions over transesterification ones, up to high monomer conversion.
Details
- Language :
- English
- ISSN :
- 0947-6539
- Volume :
- 9
- Issue :
- 18
- Database :
- MEDLINE
- Journal :
- Chemistry (Weinheim an der Bergstrasse, Germany)
- Publication Type :
- Academic Journal
- Accession number :
- 14502620
- Full Text :
- https://doi.org/10.1002/chem.200304769